Development and Field Application of Microbubble Flooding Technology for Enhanced Oil Recovery in Low-Permeability Reservoirs

Abstract For low-permeability oilfields, conventional water flooding has low sweep efficiency due to reservoir heterogeneity. Uneven flood, water channeling, crossflow, and preferential flow of fluid to relatively high permeability regions lead to low oil recovery. Targeting the sweeping control issue in low-perm. reservoir, Microbubble flooding technology (MBF) could enlarge sweep volume and increase microscopic oil-flood efficiency, effectively improving water flooding performance. Microbubble is formed by using water as continuous phase and gas as dispersing phase. Bubbles are scattered discretely in water phase with Gas/Water ratio less than 1/2. In-lab investigations on flow characteristics, microfluidics behaviors, dispersion simulation, and core flood tests have been conducted systematically, which provide solid elaboration of EOR mechanisms. In recent years, several MBF pilot tests were implemented in certain low-perm. oilfields. After more than ten-year development and field applications, MBF became one of the most promising EOR choices for low-perm. reservoir development. By Jamin effect, microbubble could divert fluid direction to relatively low-perm. regions, apparently expand sweep volume and decrease remaining oil saturation. Furthermore, through macroscopic fluctuation, interface adsorption, differential utilization of gas elastic energy, and microbubble vibration, oil-flood efficiency could also be improved by microbubble. In-lab MBF core flood tests obtained 12.6% to 24.9% incremental RF after water flooding, demonstrating very promising technical potential. Through consecutive lab study and continuous field test practices, integrated techniques, such as lab evaluation standards, reservoir selection criteria, microbubble generation equipment, surface engineering, and injection craft have been successfully developed. Microbubble flooding was successfully applied in an ultralow permeability sandstone reservoir, with effective period more than 2 years. The natural decline of the pilot well group reduced from 14.2% to -1.9%, water cut rise rate decreased from 9.9% to -1.0%, with overall incremental oil 8022 MT and a water cut reduction of 4%. As a kind of cost effective and environment friendly EOR method, MBF has great technical potential for performance improvement of water flooding. In this paper, lab tests on microbubble flooding were elaborated. Pilot test performance result from a typical low-perm. sandstone reservoir was demonstrated.